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A. Field of the Invention
The present invention relates to cable modems and, more particularly, with communicating with a cable modem with telephony return.
B. Description of Related Art and Advantages of the Invention
The growth of the cable television (CATV) industry has provided an infrastructure of high frequency coaxial (HFC) cables connected to the homes of subscribers. This availability and the high bandwidth offered by HFC cables make the cable infrastructure a desirable medium for data networks. Cable modems permit users of data networks to exploit the high-speed capabilities of HFC cables using data over cable services.
Cable modems may be bi-directional or telephony return (Telco-return) cable modems. Bi-directional modems connect to HFC networks with the capability of sending and receiving data over the coaxial cable. Because CATV has been implemented as a, uni-directional communication system, bi-directional cable modems are not widely available. Telco-return cable modems use the uni-directional communication as a downstream (data sent to the subscriber) connection, but add a telephone (PSTN) connection as an upstream (data sent from the subscriber) connection.
Telco-return cable modems provide a downstream connection with data rates as high as 30 MHz, which is much higher than the data rates available over the PSTN upstream connection. Many applications make advantageous use of telco-return cable modems. For example, web browsers, such as Netscape.TM., involve high-volume data transfers from the web site to the user and a low-volume data transfer from the user to the web site. Moreover, telco-return cable modem connections may be implemented easily using the present CATV cable infrastructure.
One problem with the telco-rectum cable modem is that the use of two different interfaces (a coaxial cable interface and a telephone interface) complicates the development of drivers and other software components that use the cable modems. Facilities are available in operating systems to implement drivers according to device type. The facilities typically use the same type of device for sending and receiving data and implement only one driver for each device. In applications that communicate over the Internet, only one IP address is needed for each driver. Because Telco-return cable modems use two types of devices, applications may have to set up two different drivers for one cable modem connection. This increases the complexity of applications because it requires applications to maintain two drivers for each cable modem connection. In addition, it makes it difficult to a single IP address for one cable modem connection.
It would be desirable to communicate with the cable modem as one driver. It would be further desirable to have the same IP address in the upstream and downstream directions.